Summary:

Beneath Philadelphia's streets lies a chaotic underground world of tunnels, pipes, and sewers that has been built over 300 years with little to no planning. Since many records were either lost or never kept in the first place, authorities are unaware of what exists down there. This lack of knowledge is not just annoying, it can be dangerous. Broken pipes often lead to sinkholes that swallow vehicles and have even caused deaths.

To deal with this, engineers rely on technologies such as robotic systems equipped with lasers and sonar to detect damage. However, finding problems is only half the challenge. Repairing them without digging up the city requires creative methods, like inserting tubes filled with liquid plastic to old pipes and hardening them with heat to create a new pipe. This technique has already been used successfully beneath the White House.

But still, Philadelphia's underground remains largely a mystery and much more exploration is still needed.

Key grammar point from the original text (KGP):

[Even if records were kept, they may be of no help.]

be of + (no) Noun = Having (or not having) the quality.

Ex:  Be of no help =  Not helpful / Be of value = Valuable